WO2012121145A1

WO2012121145A1 - Electrode active material, electrode, and secondary battery

Info

Publication number: WO2012121145A1
Application number: PCT/JP2012/055390
Authority: WO
Inventors: 佐藤　正春; 慎一中辻
Original assignee: 株式会社村田製作所
Priority date: 2011-03-10
Filing date: 2012-03-02
Publication date: 2012-09-13
Also published as: JPWO2012121145A1

Abstract

Electrode active material has an organic compound as a principal constituent thereof that contains a napthalene imide structure represented by the general formula as a constitutional unit thereof. This napthalene imide structure contains a plurality of substituents=X that are bonded by double bonds. =O is preferable for the substituents=X. It is possible to use an optional substituent for R₁-R₆, but it is preferable for R₅ and/or R₆ to be a stable radical. As a result, it is possible to achieve a secondary battery that exhibits high energy density and high output, has a long life, and exhibits favorable cycling properties in that there is little capacity decline even after repeated charging/discharging.

Description

Electrode active material, electrode, and secondary battery

The present invention relates to an electrode active material, an electrode, and a secondary battery, and more particularly to an electrode active material that repeatedly charges and discharges using a battery electrode reaction, an electrode using the electrode active material, and a secondary battery.

With the expansion of the market for portable electronic devices such as mobile phones, notebook computers and digital cameras, cordless power supplies for these electronic devices have a high energy density and high output, and long-life secondary batteries are expected.

In order to meet such demands, secondary batteries using an alkali metal ion such as lithium ion as a charge carrier and utilizing an electrochemical reaction accompanying the charge transfer have been developed. In particular, lithium ion secondary batteries have a high energy density and are becoming widespread as in-vehicle batteries.

By the way, of the constituent elements of the secondary battery, the electrode active material is a substance that directly contributes to the battery electrode reaction such as the charge reaction and the discharge reaction, and has the central role of the secondary battery. That is, the battery electrode reaction is a reaction that occurs with the transfer of electrons by applying a voltage to an electrode active material that is electrically connected to an electrode disposed in the electrolyte, and proceeds during charging and discharging of the battery. To do. Therefore, as described above, the electrode active material has a central role of the secondary battery in terms of system.

In the lithium ion secondary battery, a lithium-containing transition metal oxide is used as a positive electrode active material, a carbon material is used as a negative electrode active material, and an insertion reaction and a desorption reaction of lithium ions with respect to these electrode active materials are used. Charging / discharging.

However, the lithium ion secondary battery has a problem in that the speed of charging and discharging is limited because the movement of lithium ions in the positive electrode is rate limiting. That is, in the above-described lithium ion secondary battery, the migration rate of lithium ions in the transition metal oxide of the positive electrode is slower than that of the electrolyte and the negative electrode, and therefore the battery reaction rate at the positive electrode becomes the rate-determining rate. As a result, there is a limit to increasing the output and shortening the charging time.

Therefore, in order to solve these problems, research and development of secondary batteries using organic radical compounds, organic sulfur compounds, and quinone compounds as electrode active materials have been actively conducted in recent years.

For example, Patent Document 1 is known as a prior art document using an organic radical compound as an electrode active material.

Patent Document 1 discloses a secondary battery active material using a nitroxyl radical compound, an oxy radical compound, and a nitrogen radical compound having a radical on a nitrogen atom.

In organic radical compounds, the unpaired electrons that react are localized in the radical atoms, so that the concentration of the reaction site can be increased, and thus a high-capacity secondary battery can be realized. Further, since the reaction rate of radicals is high, it is considered that the charging time can be completed in a short time by performing charging / discharging utilizing a redox reaction of a stable radical.

And in this patent document 1, the Example using a highly stable nitroxyl radical as a radical is described, for example, the electrode layer containing a nitronyl nitroxide compound is used as a positive electrode, and lithium bonding copper foil is used as a negative electrode. When a secondary battery was produced and repeatedly charged and discharged, it was confirmed that charging and discharging were possible over 10 cycles.

Also, Patent Documents 2 and 3 are known as prior art documents using an organic sulfur compound as an electrode active material.

Patent Document 2 discloses a novel organic sulfur compound, which is a positive electrode material, has an SS bond in a charged state, and the SS bond is cleaved during discharge of the positive electrode to form an organic sulfur metal salt having a metal ion. Metal-sulfur battery cells have been proposed.

In this Patent Document 2, a disulfide organic compound represented by the general formula (1 ′) (hereinafter referred to as “disulfide compound”) is used as the organic sulfur compound.

RSSR (1 ')
Here, R represents an aliphatic organic group or an aromatic organic group, and each includes the same or different cases.

The disulfide compound can undergo a two-electron reaction, and the S—S bond is cleaved in a reduced state (discharge state), thereby forming an organic thiolate (RS—). This organic thiolate forms an S—S bond in the oxidized state (charged state) and is restored to the disulfide compound represented by the general formula (1 ′). In other words, since the disulfide compound forms an SS bond having a small binding energy, a reversible redox reaction occurs using the bond and cleavage by the reaction, and thus charge and discharge can be performed.

Patent Document 3 discloses the following formula (2 ′):
-(NH-CS-CS-NH) (2 ')
A battery electrode containing rubeanic acid or a rubeanic acid polymer that has a structural unit represented by the formula (II) and can be bonded to lithium ions has been proposed.

The rubeanic acid or rubeanic acid polymer containing the dithione structure represented by the general formula (2 ′) binds to lithium ions during reduction, and releases the bound lithium ions during oxidation. Charging / discharging can be performed by utilizing such a reversible oxidation-reduction reaction of rubeanic acid or rubeanic acid polymer.

In Patent Document 3, when rubeanic acid is used as the positive electrode active material, a two-electron reaction is possible, and a secondary battery having a capacity density of 400 Ah / kg at room temperature is obtained.

Further, Patent Document 4 is known as a prior art document using a quinone compound as an electrode active material.

Patent Document 4 proposes an electrode active material containing a specific phenanthrenequinone compound having two quinone groups in the ortho-positional relationship.

The specific phenanthrenequinone compound described in Patent Document 4 can cause a two-electron reaction peculiar to the quinone compound between the mobile carrier and a reversible oxidation-reduction reaction. Furthermore, the specific phenanthrenequinone compound is oligomerized or polymerized to achieve insolubilization in an organic solvent without causing a decrease in the number of reaction electrons due to repulsion between electrons. Patent Document 4 shows that the phenanthrenequinone dimer exhibits two oxidation-reduction voltages (around 2.9 V and around 2.5 V), and the initial discharge capacity reaches 200 Ah / kg.

JP 2004-207249 A (paragraph numbers [0278] to [0282]) US Pat. No. 4,833,048 (Claim 1, column 5, line 20 to column 28) JP 2008-147015 A (Claim 1, paragraph number [0011], FIG. 3, FIG. 5) JP 2008-222559 A (Claim 4, paragraph numbers [0027] and [0033], FIGS. 1 and 3)

However, in Patent Document 1, although an organic radical compound such as a nitroxyl radical compound is used as an electrode active material, the charge / discharge reaction is limited to a one-electron reaction involving only one electron. That is, in the case of an organic radical compound, when a multi-electron reaction involving two or more electrons is caused, the radical lacks stability and decomposes, and the radical disappears and the reversibility of the charge / discharge reaction is lost. . For this reason, the organic radical compound as in Patent Document 1 must be limited to a one-electron reaction, and it is difficult to realize a multi-electron reaction that can be expected to have a high capacity.

In Patent Document 2, a low-molecular disulfide compound in which two electrons are involved is used. However, since it repeatedly binds and cleaves with other molecules along with the charge / discharge reaction, it lacks stability, and charge / discharge reaction is not performed. If it is repeated, the capacity may decrease.

In Patent Document 3, a rubeanic acid compound containing a dithione structure is used to cause a two-electron reaction. However, when a polymer compound such as a rubeanic acid polymer is used, an intermolecular interaction in the rubeanic acid polymer is performed. As a result of the large action and hindering the movement of ions, a sufficient reaction rate could not be obtained. For this reason, it took a long time to charge. In addition, since the movement of ions is hindered as described above, the proportion of active materials that can be effectively used is reduced, and thus it has been difficult to realize a secondary battery having a desired high output.

Patent Document 4 uses a phenanthrenequinone compound having two quinone groups in the ortho-positional position as an electrode active material, and thus is excellent in stability, but is synthesized because it is a condensed ring compound. Difficult and capacity density is small.

Thus, conventionally, even when organic compounds such as organic radical compounds, disulfide compounds, and rubeanic acid are used as electrode active materials, it is difficult to achieve both multi-electron reaction and stability against charge / discharge cycles. At present, an electrode active material having a large energy density, high output, good cycle characteristics and long life has not been realized.

The present invention has been made in view of such circumstances. An electrode active material having a large energy density, high output, good cycle characteristics with little decrease in capacity even after repeated charge and discharge, and a long life. An object is to provide an electrode and a secondary battery using the substance.

The inventors of the present invention conducted intensive research to achieve the above object, and the naphthalene diimide structure is excellent in chemical stability. Since it is possible to introduce a plurality of active double bonds, it is possible to increase the capacity density of the electrode active material, thereby producing an electrode active material with high output, long life and good cycle characteristics. The knowledge that it can be obtained was obtained.

The present invention has been made based on such knowledge, the electrode active material according to the present invention is an electrode active material used as an active material of a secondary battery that repeats charge and discharge by a battery electrode reaction, The naphthalenediimide structure is mainly composed of an organic compound containing a naphthalenediimide structure in a structural unit, and the naphthalenediimide structure contains a plurality of substituents = X bonded by double bonds.

Also, in the electrode active material of the present invention, the organic compound has the general formula

It is preferable to be represented by.

In the formula, R ₁ to R ₆ are a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted cycloalkyl group. Substituted or unsubstituted alkoxyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted aryloxy group, substituted or unsubstituted arylamino group, substituted or unsubstituted alkylamino group, substituted or unsubstituted thioaryl Group, substituted or unsubstituted thioalkyl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted formyl group, substituted or unsubstituted silyl group, substituted or unsubstituted boryl group, substituted or unsubstituted stannyl group Substituted or unsubstituted cyano group, substituted or unsubstituted nitro group, substituted or unsubstituted Unsubstituted nitroso group, substituted or unsubstituted amino group, substituted or unsubstituted imino group, substituted or unsubstituted carboxyl group, substituted or unsubstituted alkoxycarbonyl group, halogen atom, stable radical group, substituted or unsubstituted Ester group, substituted or unsubstituted thioester group, substituted or unsubstituted ether group, substituted or unsubstituted thioether group, substituted or unsubstituted amine, substituted or unsubstituted amide group, substituted or unsubstituted sulfonyl group Substituted or unsubstituted sulfo group, substituted or unsubstituted thiosulfonyl group, substituted or unsubstituted sulfonamido group, substituted or unsubstituted imine, substituted or unsubstituted azo group, substituted or unsubstituted alkylene group, And a substituted or unsubstituted arylene group Showed at least one kind, substituent = X includes a case where the same or different, R 1 _~ R ₆ contains when they form a ring of the same case and connected to each other saturated or unsaturated.

Further, in the electrode active material of the present invention, the substituent = X is

It is preferable that at least one kind is selected from the group represented by.

Here, R ₇ to R ₉ are each a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted cycloalkyl group, a substituted Or an unsubstituted alkoxyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylamino group, a substituted or unsubstituted alkylamino group, a substituted or unsubstituted thioaryl group, Substituted or unsubstituted thioalkyl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted formyl group, substituted or unsubstituted silyl group, substituted or unsubstituted boryl group, substituted or unsubstituted stannyl group, substituted Or unsubstituted cyano group, substituted or unsubstituted nitro group, substituted or unsubstituted Nitroso group, a substituted or unsubstituted amino group, a substituted or unsubstituted imino group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted alkoxycarbonyl group, and represents at least one kind of halogen atom, R ₇ R ₉ includes the same case and the case where they are connected to each other to form a saturated or unsaturated ring.

In the electrode active material of the present invention, the substituent = X is more preferably = O.

Thus, when the substituent = X is formed of = O, the charge / discharge voltage can be further increased, and a suitable electrode active material can be obtained by increasing the energy density of the secondary battery.

In addition, as a result of intensive studies by the present inventors, 2,2,6,6-tetramethylpiperidine-1-oxyl (hereinafter referred to as “TEMPO”) and 2,2,5,5 are added to the N atom of the naphthalene diimide structure. By combining a compound containing a stable radical group such as 5-tetramethylpiperidin-1-yloxy (hereinafter referred to as “PROXYL”), the charging / discharging current is further increased, and charging / discharging is performed repeatedly. It was found that the discharge stability can be further improved.

That is, in the electrode active material of the present invention, it is preferable that at least one of R ₅ and R ₆ contains the stable radical group.

In the electrode active material of the present invention, it is preferable that the stable radical group contains at least one of TEMPO and PROXYL.

In this way, by binding a compound containing a stable radical group (eg, TEMPO, PROXYL) to N of the naphthalene diimide structure, the charge / discharge current is further increased, and the charge / discharge is further repeated at the time of repeated charge / discharge. Stability can be improved.

The electrode according to the present invention is characterized by containing any of the electrode active materials described above and a conductive material.

In the secondary battery according to the present invention, any one of the electrode active materials described above is included in at least one of a reaction starting material, a product, and an intermediate product in a discharge reaction of the battery electrode reaction. It is a feature.

Furthermore, the secondary battery according to the present invention has a positive electrode, a negative electrode, and an electrolyte, and the positive electrode contains any one of the electrode active materials described above.

According to the electrode active material of the present invention, the main component is an organic compound containing a naphthalene diimide structure in a structural unit, and the naphthalene diimide structure contains a plurality of substituents = X bonded by double bonds. Therefore, the naphthalene diimide structure is excellent in chemical stability and contributes to the stability improvement during charging and discharging, and since multiple electrochemically active double bonds are introduced, the high activity of the electrode active material Capacitance density can be increased, whereby an electrode active material with high output, long life, and good cycle characteristics can be obtained.

Moreover, according to the electrode of the present invention, since the electrode active material and the conductive material described in any of the above are contained, an electrode that has a stable charge / discharge reaction, a long life, and a high output can be obtained. Obtainable.

Furthermore, according to the secondary battery of the present invention, any one of the electrode active materials described above is included in at least one of reaction starting materials, products, and intermediate products in the discharge reaction of the battery electrode reaction. It is possible to obtain a secondary battery with a long life with high energy density, quick charge, discharge at high power, good cycle characteristics with little decrease in capacity even after repeated charge and discharge, and stable battery characteristics. It becomes.

In addition, since the electrode active material is mainly composed of the organic compounds described above, a secondary battery with low environmental impact and safety can be obtained.

It is sectional drawing which shows one Embodiment of the coin-type battery as a secondary battery which concerns on this invention.

Next, an embodiment of the present invention will be described in detail.

The electrode active material of the present invention contains an organic compound represented by the general formula (1) as a main component in the structural unit.

Here, R ₁ to R ₆ are each a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted cycloalkyl group, substituted or unsubstituted Unsubstituted alkoxyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted aryloxy group, substituted or unsubstituted arylamino group, substituted or unsubstituted alkylamino group, substituted or unsubstituted thioaryl group, substituted Or an unsubstituted thioalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted formyl group, a substituted or unsubstituted silyl group, a substituted or unsubstituted boryl group, a substituted or unsubstituted stannyl group, substituted or Unsubstituted cyano group, substituted or unsubstituted nitro group, substituted or unsubstituted Nitroso group, substituted or unsubstituted amino group, substituted or unsubstituted imino group, substituted or unsubstituted carboxyl group, substituted or unsubstituted alkoxycarbonyl group, halogen atom, stable radical group, substituted or unsubstituted ester Group, substituted or unsubstituted thioester group, substituted or unsubstituted ether group, substituted or unsubstituted thioether group, substituted or unsubstituted amine, substituted or unsubstituted amide group, substituted or unsubstituted sulfonyl group, substituted Or an unsubstituted sulfo group, a substituted or unsubstituted thiosulfonyl group, a substituted or unsubstituted sulfonamido group, a substituted or unsubstituted imine, a substituted or unsubstituted azo group, a substituted or unsubstituted alkylene group, and a substituted Or a small number selected from unsubstituted arylene groups It shows any one even phrases.

Further, the substituents = X include the same or different cases, and R ₁ to R ₆ include the same case and the case where they are connected to each other to form a saturated or unsaturated ring.

That is, the electrode active material of the present invention is mainly composed of an organic compound containing a naphthalene diimide structure in a structural unit, and the naphthalene diimide structure contains a plurality of substituents = X bonded by double bonds. ing.

Thus, since the electrode active material is excellent in chemical stability and contains a naphthalenediimide structure in the structural unit, stability during charge and discharge can be improved. In addition, since a plurality of electrochemically active double bonds are introduced, an electrode active material having high reactivity with cations such as lithium ions, high charge / discharge efficiency, and high capacity density can be obtained. As a result, an electrode active material having a high output, a long life and good cycle characteristics can be obtained.

Therefore, a secondary battery using such an electrode active material has a cycle with improved stability during charge / discharge, high energy density, high power discharge, and reduced capacity even after repeated charge / discharge. It is possible to obtain a secondary battery having good characteristics and stable battery characteristics and having a long life.

The electrode active material of the present invention has a high capacity density by containing a plurality of substituents = X bonded to the naphthalene diimide structure by double bonds as described above in the structural unit. Therefore, if this condition is satisfied, the type of substituent = X is not particularly limited, but is preferably selected from at least one of the groups represented by the following (2a) to (2j) Is done.

R ₇ to R ₉ in the above (2i) and (2j) are each a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted cyclohexane. Alkyl group, substituted or unsubstituted alkoxyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted aryloxy group, substituted or unsubstituted arylamino group, substituted or unsubstituted alkylamino group, substituted or unsubstituted Thioaryl group, substituted or unsubstituted thioalkyl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted formyl group, substituted or unsubstituted silyl group, substituted or unsubstituted boryl group, substituted or unsubstituted Stannyl group, substituted or unsubstituted cyano group, substituted or unsubstituted nitro group, substituted Or an unsubstituted nitroso group, a substituted or unsubstituted amino group, a substituted or unsubstituted imino group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted alkoxycarbonyl group, and a halogen atom. Can be used.

R ₇ to R ₉ include the same case and the case where they are connected to each other to form a saturated or unsaturated ring.

Among the substituents = X, ═O represented by (2a) is particularly preferable. By using ═O as the substituent = X, the charge / discharge voltage can be further increased, and the secondary battery A suitable electrode active material can be obtained by increasing the energy density.

Further, as the organic compound belonging to the category of the general formula (1), those within the above-mentioned range are preferable, and in particular, either one or both of R ₅ and R ₆ are TEMPO radical, PROXYL radical, nitro. More preferably, it contains a stable radical group such as a nilnitroxyl radical.

In other words, organic compounds belonging to the category of general formula (1) include organic compounds represented by chemical formulas (4a) to (4g) in which one or both of R ₅ and R ₆ are formed by TEMPO radicals represented by chemical formula (3). It is preferable to use an organic compound represented by the chemical formula (6) containing a compound or a PROXYL radical represented by the chemical formula (5).

Chemical reaction formula (7) shows the charge / discharge reaction of the electrode active material containing a stable radical group in the structural unit. This electrode active material forms a complex salt with the battery electrode reaction. When an organic compound in which one of R ₅ and R ₆ is composed of a TEMPO radical and the other is composed of a methyl group is used as the electrode active material and Li is used as the cation of the electrolyte salt, the chemical reaction formula (7) It is considered that the charge / discharge reaction as shown in FIG.

That is, when a stable radical group such as a TEMPO-based radical is bonded to an N atom of a naphthalenediimide structure in an electrode active material, an oxidation reaction (I → II) that generates a cation and a reduction reaction that generates an anion (I → III) exists. In the oxidation reaction, one electron is involved in the reaction, and in the reduction reaction, four electrons are involved in the reaction. Therefore, at the time of charge / discharge, five electrons are involved in the reaction. It becomes possible to further improve the stability against discharge.

The electrode active material of the present invention is preferably an organic compound using a stable radical group for one or both of R ₅ and R ₆ as described above, but may be composed of other than the stable radical group. For example, the chemical formula (8a ) To (8c) can be used.

Also in this case, the electrode active material forms a complex salt with the battery electrode reaction. For example, when an organic compound in which both R ₅ and R ₆ are composed of methyl groups is used as an electrode active material and Li is used as a cation of an electrolyte salt, a charge / discharge reaction as shown in the chemical reaction formula (9) occurs. It is thought to occur.

Even in this case, it is considered that a charge / discharge reaction involving four electrons occurs between the compound (IV) and the compound (V), thereby increasing the charge / discharge capacity and improving the stability against repeated charge / discharge. Can be achieved.

The molecular weight of the organic compound constituting the electrode active material is not particularly limited, but in the case of a low molecular weight molecule having a small molecular weight, it may be easily dissolved in the electrolyte, and the molecular weight is above a certain level. Is preferred. However, the appearance of the effect desired by the present invention depends on the reactivity of a plurality of substituents = X. Therefore, when the portion other than these substituents = X becomes larger, the capacity that can be stored per unit mass, that is, the capacity density Becomes smaller.

In addition, when it uses as a polymer of the organic compound mentioned above, molecular weight and molecular weight distribution are not specifically limited.

Next, a secondary battery using the electrode active material will be described in detail.

FIG. 1 is a cross-sectional view showing a coin-type secondary battery as an embodiment of a secondary battery according to the present invention. In this embodiment, the electrode active material of the present invention is used as a positive electrode active material. ing.

The battery can 1 has a positive electrode case 2 and a negative electrode case 3, and both the positive electrode case 2 and the negative electrode case 3 are formed in a disk-like thin plate shape. In the center of the bottom of the positive electrode case 2 that constitutes the positive electrode current collector, a positive electrode 4 in which a mixture containing a positive electrode active material (electrode active material) and a conductive agent (conductive material) is formed into a sheet shape is disposed. A separator 5 formed of a porous sheet or film such as a microporous film, a woven fabric, or a nonwoven fabric is laminated on the positive electrode 4, and a negative electrode 6 is laminated on the separator 5. As the negative electrode 6, for example, a stainless steel foil or a copper foil overlaid with a lithium metal foil, or a lithium foil occlusion material such as graphite or hard carbon applied to a copper foil can be used. A negative electrode current collector 7 made of metal is laminated on the negative electrode 6, and a metal spring 8 is placed on the negative electrode current collector 7. The electrolyte 9 is filled in the internal space, and the negative electrode case 3 is fixed to the positive electrode case 2 against the urging force of the metal spring 8 and sealed with a gasket 10.

Next, an example of a method for manufacturing the secondary battery will be described in detail.

First, an electrode active material is formed into an electrode shape. For example, an electrode active material is mixed with a conductive agent and a binder, and a solvent is added to form a slurry. The slurry is applied on the positive electrode current collector by an arbitrary coating method and dried to form a positive electrode. To do.

Here, the conductive agent is not particularly limited, and examples thereof include carbonaceous fine particles such as graphite, carbon black, and acetylene black, carbon fibers such as vapor grown carbon fiber, carbon nanotube, and carbon nanohorn, polyaniline, and polypyrrole. , Conductive polymers such as polythiophene, polyacetylene, and polyacene can be used. Further, two or more kinds of conductive agents can be mixed and used. The content of the conductive agent in the positive electrode 4 is desirably 10 to 80% by mass.

Also, the binder is not particularly limited, and various resins such as polyethylene, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyethylene oxide, carboxymethylcellulose, and the like can be used.

Further, the solvent is not particularly limited, and examples thereof include basic solvents such as dimethyl sulfoxide, dimethylformamide, 1-methyl-2-pyrrolidone, propylene carbonate, diethyl carbonate, dimethyl carbonate, and γ-butyrolactone, acetonitrile, Nonaqueous solvents such as tetrahydrofuran, nitrobenzene, and acetone, protic solvents such as methanol and ethanol, water, and the like can be used.

Also, the type of organic solvent, the compounding ratio of the organic compound and the organic solvent, the type of additive and the amount of the additive, and the like can be arbitrarily set in consideration of the required characteristics and productivity of the secondary battery. Next, the positive electrode 4 is impregnated into the electrolyte 9 so that the electrolyte 9 is impregnated with the positive electrode 4, and then the positive electrode 4 at the bottom center of the positive electrode case 2 constituting the positive electrode current collector is placed. Next, the separator 5 impregnated with the electrolyte 9 is laminated on the positive electrode 4, the negative electrode 6 and the negative electrode current collector 7 are sequentially laminated, and then the electrolyte 9 is injected into the internal space. Then, a metal spring 8 is placed on the negative electrode current collector 7, and a gasket 10 is arranged on the periphery, and the negative electrode case 3 is fixed to the positive electrode case 2 with a caulking machine or the like, and the outer casing is sealed. A type secondary battery is produced.

Incidentally, the electrolyte 9 interposed between the negative electrode 6, which is a counter electrode of the positive electrode 4 and the positive electrode 4 performs a charge carrier transport between the electrodes, but as such a electrolyte 9, at room temperature for 10 ^- Those having an ionic conductivity of ⁵ to 10 ⁻¹ S / cm can be used. For example, an electrolytic solution in which an electrolyte salt is dissolved in an organic solvent can be used.

Here, as the electrolyte salt, for example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ or the like can be used.

As the organic solvent, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide, dimethylacetamide, 1-methyl-2-pyrrolidone, etc. are used. be able to.

Further, a solid electrolyte may be used as the electrolyte 9. Examples of the polymer compound used in the solid electrolyte include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-monofluoroethylene copolymer, and fluoride compound. Vinylidene fluoride polymers such as vinylidene-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and acrylonitrile-methyl methacrylate copolymer Polymer, acrylonitrile-methyl acrylate copolymer, acrylonitrile-ethyl methacrylate copolymer, acrylonitrile-ethyl acrylate copolymer, acrylonitrile-methacrylic acid copolymer, acrylonitrile-acrylic Examples thereof include acrylonitrile polymers such as phosphoric acid copolymers, acrylonitrile-vinyl acetate copolymers, polyethylene oxide, ethylene oxide-propylene oxide copolymers, and polymers of these acrylates and methacrylates. it can. Further, these polymer compounds containing an electrolytic solution in a gel form may be used as the electrolyte 9 or only a polymer compound containing an electrolyte salt may be used as the electrolyte 9 as it is.

Thus, since the electrode of the present invention contains the electrode active material and the conductive material described above, the charge / discharge efficiency is good, the battery can be charged in a short time, and the output can be increased.

In addition, since the electrode active material of the secondary battery is reversibly oxidized or reduced by charge and discharge, it has a different structure and state in the charged state, the discharged state, or the state in the middle thereof. The electrode active material is contained in at least one of a reaction starting material in a discharge reaction (a material that causes a chemical reaction in a battery electrode reaction), a product (a material resulting from a chemical reaction), and an intermediate product. . As a result, a long-life secondary battery having a large energy density, capable of being charged quickly, capable of discharging at a high output, having good cycle characteristics with little decrease in capacity even after repeated charge and discharge, and having stable battery characteristics is obtained. It becomes possible.

In addition, the secondary battery of the present invention has at least two discharge voltages in the discharge reaction, thereby realizing a high-capacity density secondary battery across a plurality of voltages.

Moreover, since the electrode active material is mainly composed of organic compounds, it is possible to obtain a secondary battery with low environmental impact and safety.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the above-listed chemical formulas (4a) to (4g), (6), and (8a) to (8c) are examples of the organic compounds that are the main components of the electrode active material. is not. That is, if the main component is an organic compound containing a naphthalene diimide structure in a structural unit, and the naphthalene diimide structure contains a plurality of substituents = X bonded by double bonds, the above chemistry Like the reaction formula (7) or (9), since the battery electrode reaction proceeds, the stability of the charge / discharge reaction is improved, the energy density is large, and the desired secondary battery having excellent stability can be obtained. It becomes.

In this embodiment, the coin-type secondary battery has been described. However, it is needless to say that the battery shape is not particularly limited, and can be applied to a cylindrical type, a square type, a sheet type, and the like. Also, the exterior method is not particularly limited, and a metal case, mold resin, aluminum laminate film, or the like may be used.

In this embodiment, the electrode active material is used as the positive electrode active material, but it is also useful to use it as the negative electrode active material.

Next, specific examples of the present invention will be described.

In addition, the Example shown below is an example and this invention is not limited to the following Example.

[Synthesis of organic compounds]
According to the following synthesis scheme (A), compound 4a containing naphthalenediimide in the structural unit was synthesized.

First, 1.77 mmol naphthalene-1,4,5,8-tetracarboxylic dianhydride (4a ₁ ), 1.77 mmol 4-amino TEMPO (4a ₂ ) and 3.57 mmol 4-fluoroaniline (4a ₃ ) was dissolved in 10 mL of dimethylacetamide (hereinafter referred to as “DMA”), an acid was added, and the mixture was stirred at 100 ° C. for 3 hours. The solution was concentrated under reduced pressure and the resulting precipitate was filtered. The crude product thus obtained was separated by silica gel chromatography, and the solid obtained from the main fraction was recrystallized from a mixed solvent of dichloromethane / methanol to obtain orange needle crystals.

And when this acicular crystal was measured by infrared absorption spectrum, it was confirmed from the measurement result that this acicular crystal was compound 4a.

[Production of secondary battery]
Compound 4a as a positive electrode active material (electrode active material): 300 mg, graphite powder as a conductive agent: 600 mg, and polytetrafluoroethylene as a binder: 100 mg were weighed and kneaded while mixing uniformly. Produced. Subsequently, this mixture was pressure-molded to obtain a sheet-like member having a thickness of about 150 μm. Thereafter, this sheet-like member was dried in a vacuum at 70 ° C. for 1 hour, and then punched into a circle having a diameter of 12 mm to produce a positive electrode containing Compound A. Next, the positive electrode was impregnated with the electrolytic solution, and the electrolytic solution was infiltrated into the voids in the positive electrode. Here, as the electrolytic solution, a mixed solution in which LiPF ₆ was dissolved in an organic solvent, ethylene carbonate / diethyl carbonate, so that the molar concentration of LiPF ₆ (electrolyte salt) was 1.0 mol / L was used. The mixing ratio of ethylene carbonate and diethyl carbonate was ethylene carbonate: diethyl carbonate = 30: 70 in volume%.

Next, this positive electrode was placed on a positive electrode current collector, and a separator having a thickness of 20 μm made of a polypropylene porous film impregnated with the electrolytic solution was further laminated on the positive electrode, and further a stainless steel current collector plate The negative electrode which stuck lithium on both surfaces was laminated | stacked on the separator. Then, a metal spring is placed on the current collector, and the negative electrode case is joined to the positive electrode case with a gasket provided on the periphery, and the outer case is sealed by a caulking machine, and the compound 4a, the negative electrode is used as the positive electrode active material. A sealed coin-type battery having metallic lithium as an active material was produced.

[Confirmation of secondary battery operation]
The coin-type battery produced as described above was charged with a constant current of 0.1 mA until the voltage reached 4.0 V, and then discharged with a constant current of 0.1 mA until it reached 1.5 V. As a result, it was confirmed that this battery was a secondary battery having a discharge capacity of 0.33 mAh having a plurality of voltage flat portions at a charge / discharge voltage of 1.5 to 3.2 V.

When the discharge capacity was calculated, the capacity density per mass of the electrode active material was 260 Ah / kg, and it was found that the compound 4a was a high capacity density electrode active material.

Thereafter, charging and discharging were repeated 10 cycles in the range of 1.5 to 3.8V. As a result, it was found that the secondary battery had a long cycle life of 50% or more of the initial value even after 10 cycles, and little decrease in capacity even after repeated charge and discharge.

[Synthesis of organic compounds]
According to the following synthesis scheme (B), compound 4b containing naphthalenediimide in the structural unit was synthesized.

First, 1.77 mmol naphthalene-1,4,5,8-tetracarboxylic dianhydride (4b ₁ ), 1.77 mmol 4-amino TEMPO (4b ₂ ) and 3.57 mmol 2,4,6- Fluoroaniline (4b ₃ ) was dissolved in 10 mL of DMA, and then Compound 4b was produced by the same method and procedure as in Example 1.

[Production of secondary battery]
A coin-type battery was produced in the same manner as in Example 1 except that the compound 4b was used as the positive electrode active material instead of the compound 4a in Example 1.

[Confirmation of secondary battery operation]
The coin-type battery was charged with a constant current of 0.1 mA until the voltage reached 3.8 V, and then discharged to 1.5 V with a constant current of 0.1 mA. As a result, it was confirmed that this battery was a secondary battery having a discharge capacity of 0.25 mAh having a plurality of voltage flat portions at a charge / discharge voltage of 2.0 to 2.8V.

[Synthesis of organic compounds]
According to the following synthesis scheme (C), compound 4c containing naphthalenediimide in the structural unit was synthesized.

First, 1.77 mmol of naphthalene-1,4,5,8-tetracarboxylic dianhydride (4c ₁ ), 1.77 mmol of 4-amino TEMPO (4c ₂ ) and 3.57 mmol of (E) -4- (2-Phenylazenyl) benzenamine (4c ₃ ) was dissolved in 10 mL of DMA, and then Compound 4c was prepared by the same method and procedure as in Example 1.

[Production of secondary battery]
A coin-type battery was produced in the same manner as in Example 1 except that the compound 4c was used as the positive electrode active material instead of the compound 4a in Example 1.

Thereafter, charging and discharging were repeated 10 cycles in the range of 1.5 to 3.8V. As a result, it was found that the secondary battery had a long cycle life of 50% or more of the initial value even after 10 cycles, and little reduction in capacity even after repeated charge and discharge.

[Synthesis of organic compounds]
According to the following synthesis scheme (D), compound 4d containing naphthalenediimide in the structural unit was synthesized.

First, 1.77 mmol naphthalene-1,4,5,8-tetracarboxylic dianhydride (4d ₁ ), 1.77 mmol 4-amino TEMPO (4d ₂ ) and 3.57 mmol 2-aminoacetic acid (4d ₃ ) was dissolved in 10 mL of DMA, and then Compound 4d was prepared by the same method and procedure as in Example 1.

[Production of secondary battery]
A coin-type battery was produced in the same manner as in Example 1 except that the compound 4d was used as the positive electrode active material instead of the compound 4a in Example 1.

[Confirmation of secondary battery operation]
The coin-type battery was charged with a constant current of 0.1 mA until the voltage reached 3.8 V, and then discharged with a constant current of 0.1 mA to 1.5 V. As a result, it was confirmed that this battery was a secondary battery having a discharge capacity of 0.25 mAh having a plurality of voltage flat portions at a charge / discharge voltage of 2.0 to 2.8V.

[Synthesis of organic compounds]
According to the following synthesis scheme (E), compound 4e containing naphthalenediimide in the structural unit was synthesized.

First, 1.77 mmol naphthalene-1,4,5,8-tetracarboxylic dianhydride (4e ₁ ), 1.77 mmol 4-amino TEMPO (4e ₂ ) and 3.57 mmol 3-aminopropanoic acid ( 4e ₃ ) was dissolved in 10 mL of DMA, and then Compound 4e was produced by the same method and procedure as in Example 1.

[Production of secondary battery]
A coin-type battery was produced in the same manner as in Example 1, except that the compound 4e was used as the positive electrode active material instead of the compound 4a in Example 1.

[Confirmation of secondary battery operation]
The coin-type battery was charged with a constant current of 0.1 mA until the voltage reached 3.8 V, and then discharged to 1.5 V with a constant current of 0.1 mA. As a result, it was confirmed that this battery was a secondary battery having a discharge capacity of 0.24 mAh having a plurality of voltage flat portions at a charge / discharge voltage of 2.0 to 2.8 V.

する Realizes a stable secondary battery with high energy density, high output, good cycle characteristics with little decrease in capacity even after repeated charge and discharge.

4 Positive electrode 6 Negative electrode 9 Electrolyte

Claims

An electrode active material used as an active material of a secondary battery that repeats charging and discharging by a battery electrode reaction,
An electrode active material comprising an organic compound containing a naphthalenediimide structure in a constituent unit as a main component, and the naphthalenediimide structure containing a plurality of substituents = X bonded by double bonds .
The organic compound has the general formula

[Wherein R 1 to R 6 are a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted cycloalkyl group. Substituted or unsubstituted alkoxyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted aryloxy group, substituted or unsubstituted arylamino group, substituted or unsubstituted alkylamino group, substituted or unsubstituted thioaryl Group, substituted or unsubstituted thioalkyl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted formyl group, substituted or unsubstituted silyl group, substituted or unsubstituted boryl group, substituted or unsubstituted stannyl group Substituted or unsubstituted cyano group, substituted or unsubstituted nitro group, substituted or unsubstituted Is an unsubstituted nitroso group, substituted or unsubstituted amino group, substituted or unsubstituted imino group, substituted or unsubstituted carboxyl group, substituted or unsubstituted alkoxycarbonyl group, halogen atom, stable radical group, substituted or unsubstituted Substituted ester group, substituted or unsubstituted thioester group, substituted or unsubstituted ether group, substituted or unsubstituted thioether, substituted or unsubstituted amine, substituted or unsubstituted amide group, substituted or unsubstituted sulfonyl group Substituted or unsubstituted sulfo group, substituted or unsubstituted thiosulfonyl group, substituted or unsubstituted sulfonamido group, substituted or unsubstituted imine, substituted or unsubstituted azo group, substituted or unsubstituted alkylene group, And a substituted or unsubstituted arylene group Showed at least one kind, substituent = X includes a case where the same or different, R 1 ~ R 6 comprises a case of forming a ring of the same case and connected to each other saturated or unsaturated. ]
The electrode active material according to claim 1, wherein
The substituent = X is

[Wherein R 7 to R 9 are each a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted cycloalkyl group, a substituted Or an unsubstituted alkoxyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted arylamino group, a substituted or unsubstituted alkylamino group, a substituted or unsubstituted thioaryl group, Substituted or unsubstituted thioalkyl group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted formyl group, substituted or unsubstituted silyl group, substituted or unsubstituted boryl group, substituted or unsubstituted stannyl group, substituted Or unsubstituted cyano group, substituted or unsubstituted nitro group, substituted or unsubstituted Nitroso group, a substituted or unsubstituted amino group, a substituted or unsubstituted imino group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted alkoxycarbonyl group, and represents at least one kind of halogen atom, R 7 to R 9 include the same case and the case where they are connected to each other to form a saturated or unsaturated ring. ]
The electrode active material according to claim 1, wherein at least one kind is selected from the group represented by:
The electrode active material according to claim 3, wherein the substituent = X is = O.
The electrode active material according to claim 2, wherein at least one of R 5 and R 6 is the stable radical group.
The stable radical group contains at least one of 2,2,6,6-tetramethylpiperidin-1-oxyl and 2,2,5,5-tetramethylpiperidin-1-yloxy. The electrode active material according to claim 5.
An electrode comprising the electrode active material according to any one of claims 1 to 6 and a conductive material.
The electrode active material according to any one of claims 1 to 6 is contained in any one of a reaction starting material, a product, and an intermediate product in at least a discharge reaction of a battery electrode reaction. Next battery.
A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode contains the electrode active material according to any one of claims 1 to 6.